HV nanosecond pulse generation technology is based primarily on the capacitive energy storage and closing switches. The simplest example is a capacitor shorted onto a discharge load gap by a spark gap. Although abundant in laboratory use, these basic capacitive systems do not allow pulse shaping, are characterized by a ringing uncontrollable discharge and possess a short lifetime.
Capacitive sources with magnetic compression shown schematically in FIG. 1 represent advanced technology. (See e.g., Oh J. S., Cho M. H., Ko I. S., Namkung W. and Jang J. H. “Operational Characteristics of 30 kW Average MPC Modulator for Plasma DeNOx/DeSOx System”. Proc. of 11th IEEE Int. Pulsed Power Conf., Baltimore, Jun. 29-Jul. 2, 1997, pp. 1091-1096, and Druckmann I. and Smilanski I. “Operation of Two-Copper Lasers by a Single Magnetic Modulator”. Proc. of 11th IEEE Int. Pulsed Power Conf., Baltimore, Jun. 29-Jul. 2, 1997.) They can be realized with all-solid state switches having microsecond closing times, although most pulsers are thyratron-based. Magnetic switches (MS) compress a wide microsecond pulse to a desired width. Pulsers with all-solid state semiconductor and magnetic switches offer long life and have high reliability.
A serious shortcoming of pulsers like the one depicted in FIG. 1 is in the necessity of remagnetization of the cores of the magnetic switches. Another deficiency is the drop in the output voltage, when the transformer pulse is compressed during the energy transfer across the compression stages.
Another magnetic compression system is described in Rukin S. N. “Device for pulse magnetic compression”, RF Inventor's Certificate No. 2 089 042, Byul. Izobr. N. 24, 27 Aug. 1997, p. 426, filing date 29 Mar. 1993, and shown schematically in FIG. 2. This pulser, which is essentially a well-known Fitch circuit (see, e.g., Bazelyan E. M. and Raizer Yu. P. “Spark Discharge”. CRC Press, NY, 1998, 294 pp., p. 97), provides voltage multiplication and does not require costly remagnetization techniques. It operates as follows. When switch 2 closes, capacitor 1 discharges and through transformer 3 charges capacitors 7 and 8 to the shown polarities. Upon the saturation of the transformer 3 core, capacitor 7 recharges to the opposite polarity and the voltage across capacitors 7 and 8 doubles. At this moment, the core of magnetic switch 13 saturates, and the voltage is applied to magnetic switch 16 and to capacitors 9 and 10. The described process repeats itself through the number of compression stages. Similarly to the voltage doubling in the first compression stage, upon the magnetic switch 16 closure, capacitor 9 recharges to the opposite polarity, and the voltage across capacitors 9 and 10 doubles, etc. The charge path for capacitor 12 is provided by the load 4, its parasitic capacitance 5 and auxiliary inductor 6. Finally, when magnetic switch 15 closes, capacitors 11 and 12 discharge onto load 4.
The shortcoming of the described device is that in the case of a gas discharge load that is an open circuit at low voltage, e.g., a corona gap, there is no adequate path for C12 charge, and additionally, the load capacitance 5 together with inductor 6 form a resonance subcircuit, which instead of a unipolar pulse, generates ringing bipolar pulses. An accompanying disadvantage of these phenomena is a low energy efficiency of the said topology. This is illustrated by the waveforms of load voltage and current (FIG. 3) in the case of a corona discharge load (see Pokryvailo, A., Yankelevich, Y., Wolf, M., Abramzon, E., Shviro., E., Wald, S., and Wellemann, A., “A 1KW Pulsed Corona System for Pollution Control Applications”, Proc. 14th IEEE Int. Conf on Pulsed Power, Dallas, 15-18 Jun. 2003, pp. 225-228).